Sir William, who died in 1687, had bought and improved St. Catherine's Park, Leixlip, which he wished to descend to his male heirs.
[2] With his inheritance, and the friendship of James Butler, 2nd Duke of Ormonde, to whom he admitted he owed his advancement, he decided that he had sufficient wealth and influence to acquire a title.
He chose Viscount Mount Cashell, which had previously been a Jacobite title given to Catherine's uncle Justin MacCarthy, who died in 1694.
[3] Elrington Ball describes Mount Cashell as a young man of fashion, who found life in Dublin dull, and was fond of malicious gossip about his fellow peers.
On the other hand, he describes Lady Mount Cashell as a woman who was greatly esteemed for her religious devotion and acts of charity.